I'm not a hydro guy, but looks like it could be either rootbound or consistent oversaturation. (overwatering or overly humid...?)

Someone with hydro experience should be along soon with a more accurate and reliable diagnosis though.

Nice job with filling-out the form. :thumbsup:
But there is a hydro-specific troubleshooting form available. It's just below the soil form in the same thread. Might be needing some of the pertinant info from the hydro form for a proper diagnosis. <doh>